E. coli septicaemia or colibacillosis is a disease which generally occurs in poultry (such as chickens and turkeys) and which is responsible for considerable losses. Characteristic symptoms in birds having this disease are air sac inflammation, pericarditis and perihepatitis. Most of the investigations in this field reveal that more than half of the E. coli strains which are encountered in said sick birds belong to one of three serotypes 01:K1, 02:K1 or 078:K80. In the United States, the serotype 035 is also frequently encountered. It is generally assumed that E. coli septicaemia is a secondary infection which enters the body via the respiratory tract after it has been damaged, for example, by viruses which cause respiratory diseases or by mycoplasmas.
Little is known of the virulence factors which play a role in the pathogenesis of colibacillosis in poultry. The virulence factors of E. coli strains which play a role in infections in mammals include, for example, attachment fimbriae, toxins and iron-sequestrating mechanisms.
Many different attachment fimbriae, which are generally highly host-specific, have been described. Thus, the CFA fimbriae have been encountered in humans with diarrhoea. K88 fimbriae in piglets with diarrhoea, K99 in sheep, calves and piglets with diarrhoea, and P fimbriae (including those of the F11 type) in humans with urinary tract infections. It has been found, in addition, that administration of said types of attachment fimbriae in purified form as a vaccine resulted in a protective immune response in the respective type of animal. However, a similar virulence factor has not been identified for colibacillosis in poultry.